There is an ever increasing demand for communications infrastructure that can support inexpensive, high-speed communications to every residential and business address that desires it. As one example, the use of the Internet for commerce, education, entertainment, communications, and many other purposes is quickly developing. There is likewise an increasing interest in providing entertainment and other services to residential and business customers that require moving large amounts of data very quickly, i.e. that have high bandwidth requirements, such as video-on-demand, high fidelity audio, high definition television, computer software, documents, medical X-ray charts, digital photography, and the like.
It is well known to implement the needed communications infrastructure by interconnecting communications nodes using wires and cables. However, cabling is expensive and time-consuming to deploy, and it has not been able to fulfill the expanding demand for high-speed communications services.
Wireless communications systems provide a relatively low cost alternative to wire-based communications networks, and they are quicker to deploy. One known wireless network architecture is the wireless local network having one or more base stations or server nodes distributed throughout a region of system users. Each system user has wireless equipment for communicating bi-directionally with a server node. This type of wireless network is sometimes referred to as a “last mile” network, because information content can be distributed from a high bandwidth source by cable to a server node that is in the neighborhood of the system user and then distributed the “last mile” via a wireless link between the server node and the system user's equipment.
The known optical wireless local networks comprise one or more optical transmitters at a server node. The optical transmitter is generally paired with an optical receiver for receiving optical communications sent to the server node from subscriber's equipment. Pairs of the known optical transmitters and receivers handle communications over a certain angle of coverage of the subscriber area. Generally the angle of coverage is dependent upon the distance from the server node to the furthest receivers. The angle of coverage can thus be a few degrees, e.g. 5 to 10 degrees, for a subscriber area that includes distant subscribers, or it can be relatively large, e.g. 30 to 45 degrees, for a subscriber area that doesn't have any distant subscribers.
Each optical transmitter must have sufficient signal transmission power to cover all subscriber receivers within the angle of coverage out to a certain distance from the server node. In general, the higher the transmission power required of the server node's optical transmitter, the more complex and expensive the components of the optical transmitter must be. Correspondingly, the lower the field strength of the optical signal received at a subscriber's receiver, the more complex and expensive must be the components of the subscriber receiver.
Accordingly, there is a significant need for methods and apparatus that can substantially improve transmitter signal strength in an optical wireless communications system without substantially increasing the complexity and cost of the optical transmitter.